The present invention relates to polyorganosiloxane compositions capable of indicating the curing state thereof by change in color.
Addition curable liquid silicone elastomer compositions, which are already well-known, are compositions wherein curing of a polyorganosiloxane having alkenyl radicals and a polyorganohydrogensiloxane having hydrogen atoms bonded to silicon atoms is effected using a catalyst for addition reaction such as a platinum compound etc. (refer to Japanese Patent Publication No. 27853/1968)
Conventionally, in order to check the curing state of an elastomer obtained from such a liquid silicone elastomer composition, evaluation had to be made by observation, for example, through touching the silicone elastomer composition being cured or measuring penetration thereto or rubber hardness.
For example, when such liquid silicon elastomers are used for molding or as a dental impression material, operators or dentists have to touch the silicone elastomer occasionally to judge the curing state upon releasing the rubber mold from a prototype or oral cavity and keep observing the curing state of the elastomer by touching until it is releasable. Such processes have consumed much valuable time of the operators and it has often kept them from their primary diagnostic activities.
It has also happened that releasing of elastomer or the next process is conducted while the curing state of the elastomer is insufficient because the point where curing is completed may not properly be evaluated by touching, which brings about such troubles as breakage of the elastomer, sticking of the elastomer to the prototype etc.